The present invention is generally related to antennas, and more particularly to mobile communication antennas having dipole antennas, beam forming capabilities including downtilt, and reduced intermodulation (IM).
Wireless mobile communication networks continue to be deployed and improved upon given the increased traffic demands on the networks, the expanded coverage areas for service and the new systems being deployed. Cellular type communication systems derive their name in that a plurality of antenna systems, each serving a sector or area commonly referred to as a cell, are implemented to effect coverage for a larger service area. The collective cells make up the total service area for a particular wireless communication network.
Serving each cell is an antenna array and associated switches connecting the cell into the overall communication network. Typically, the antenna array is divided into sectors, where each antenna serves a respective sector. For instance, three antennas of an antenna system may serve three sectors, each having a range of coverage of about 120xc2x0. These antennas are typically vertically polarized and have some degree of downtilt such that the radiation pattern of the antenna is directed slightly downwardly towards the mobile handsets used by the customers. This desired downtilt is often a function of terrain and other geographical features. However, the optimum value of downtilt is not always predictable prior to actual installation and testing. Thus, there is always the need for custom setting of each antenna downtilt upon installation of the actual antenna. Typically, high capacity cellular type systems can require re-optimization during a 24 hour period. In addition, customers want antennas with the highest gain for a given size and with very little intermodulation (IM). Thus, the customer can dictate which antenna is best for a given network implementation.
The present invention achieves technical advantages as an air dielectric stripline feed system stamped from a sheet of metal, with one air dielectric stripline being coupled to each respective dipole radiating elements of each antenna. Each air dielectric stripline feed system is non-physically coupled to a sliding dielectric phase shifter disposed between the stripline and the groundplane and adapted to provide downtilt, while still maintaining uniform side lobes. Preferably, up to 10xc2x0 of downtilt is obtainable.
The cross-shaped unitary dipole antenna has a unitary dipole radiation element formed by folding a stamped sheet of metal. The unitary dipole radiation element is vertically polarized and has the general shape of a cross. Two radiation elements each have a 90xc2x0 bend and are commonly connected to each other at a base but are separated above a groundplane by a cross-shaped dielectric spacer. A cross-shaped, non-conductive clip is attached to the top of the antenna to maintain an orthogonal relationship between the four radiating sections of the unitary dipole antenna.